1. Field of the Invention
The present invention relates to a method of monitoring focusing condition in a semiconductor image position sensitive device (hereinafter referred to as "PSD"). More particularly, the present invention relates to a monitoring method which is suitable for use in adjusting an imaging optical system of a bright spot image position detecting apparatus which makes use of a PSD of multiple output terminal type.
2. Description of the Related Art
Conventional image position detecting apparatus incorporating a non-scan type PSD has no means which would enable monitoring of the state of focusing of a bright spot on the image detecting surface of the PSD. Therefore, the PSD is arranged merely such that its image detecting surface is positioned at the calculated imaging plane in its design. Alternatively, the optimum imaging plane is detected by a suitable means such as a scan-type image sensor and the PSD is set such that its image detecting surface is positioned in alignment with the imaging plane detected by the image sensor. It has been therefore impossible to monitor the focusing condition under the conditions of actual use.
Thus, in the known image position detecting apparatus incorporating a PSD, it has been difficult to adjust the optical system towards the best focusing, due to lack of means for monitoring the imaging condition of a bright spot on the image detecting surface of the PSD.